chart.js: hide specific ticks in y-axis and hide all x-axis grid line

Edit

I'm using charts.js library and i wanted to know if it's possible to hide specific ticks from my y-axis, for example, i have defined ticks's min:0 and max:100 and it shows all the values in multiples of ten from 0 to 100, but i want to display only 0, 50 e 100. (this is solved)

Another problem is that i wanted to remove all x-axis' gridline but method "gridLines.display : false" doesn't hide the first vertical line on the beginning of the chart, just hides the others.